Researchers Identify Novel Auxin Sensing Complex at Cell Surface of Arabidopsis

May 04, 2014     Email"> PrintText Size

Scientists have reported a novel auxin sensing complex ABP1/TMK on plasma membrane of plants, which can mediate cellular responses such as cytoskeleton organization. This elucidates the molecular mechanism how auxin determines the polarity establishment and cell shape formation.

A team of researchers from the University of California, Riverside, Shanghai Center for Plant Stress Biology, Shanghai Institutes for Biological Sciences (SIBS), and Institute of Plant Physiology& Ecology, SIBS has identified TMK family proteins, which are receptor like kinases, as co-receptors for ABP1 to transmit auxin signal to ROP small GTPase signaling cascades.

Plant hormone auxin has been the main focus of plant research since discovered by Darwin about 100 years ago. As its name implied, auxin regulates plant growth and development nearly on all aspects. In 2005, the auxin receptor TIR1 was identified in nucleus which can mediate auxin-dependent gene expression. This is a milestone finding in plant research, which unveiled the molecular mechanism of auxin signaling pathways. However, auxin receptor TIR1 is not able to explain all the action modes of auxin. ABP1, as an auxin binding protein, has been well-studied to mediate auxin responses in plants, but its role as an auxin receptor was widely doubted due to ABP1 protein does not contain any functional domains and its functional mechanism is largely unknown.  

Xu et al identified transmembrane kinase (TMK) family proteins that can interact with ABP1 and become its co-receptor to transduce auxin signals. Through biochemical and cell biological analyses, the researchers proved that auxin could work on formation of ABP1/TMK receptor complex. Most importantly, they provided the evidence that the auxin can activate ROP small GTPase signaling cascades which lead to the cytoskeleton changes. The work entitled “Cell Surface ABP1-TMK Auxin-Sensing Complex Activates ROP GTPase Signaling” has thus received a worldwide recognition in the plant community since its publication on Science in Feb 2014.  

“The finding of ABP1/TMK interacting proteins extends our knowledge of understanding auxin signaling, and opens up a new horizon in auxin biology” says Professor YANG Zhenbiao. It may lead to a new direct connection between auxin signaling components and other signaling cascades in plant cells.  

Since auxin regulates plant architecture through regulation of cell polarization, expansion, division and differentiation, the discovery of novel auxin-sensing complexes on the plasma membrane together with the underlying mechanism will be fundamental in selecting and breeding super elite crops via molecular design in the future.